Portable information apparatuses configured to be lightweight and compact in terms of portability are often limited in their functions. For example, there are cases where notebook type personal computers (laptop PCs) are limited in their functions to achieve a reduction in weight and thickness. For such a laptop PC, a docking device is provided as a dedicated device to expand the function of the laptop PC. The docking device is configured to be connected to the laptop PC via a connector to expand the function of the laptop PC. For example, in Japanese Unexamined Patent Application Publication No. 2019-61652, the present applicant has proposed a docking device including engaging members having hook portions that can engage with and disengage from an engaging hole of a portable information apparatus.